Inter-vane platform with flexible securing pins and variable shear stresses for a support disk for the vanes of a turbine engine

ABSTRACT

An inter-vane platform ( 3 ) for a vane support disk ( 1 ) of a fan of a turbine engine, comprising a deflecting part ( 4 ) includes a lower face ( 5 ) provided with at least one first securing foot ( 6 ), provided with at least one aperture ( 7 ) for the passage of a securing pin ( 8 ) intended to connect it to a second securing foot ( 12 ) of the support disk ( 1 ), between two adjacent vanes. The securing pin ( 8 ) includes a rod ( 17 ) provided with a first threaded part ( 18 ) having a first diameter (D1) chosen and intended to accommodate a nut ( 22 ) intended for the connection, and a second part ( 19 ) including a first sub-part ( 20 ) extending the first sub-part ( 18 ), having a second diameter (D2) greater than the first diameter (D1) and intended to be interlaced between the first ( 6 ) and second ( 12 ) securing feet, and a second sub-part ( 21 ) extending the first sub-part ( 20 ) and having a third diameter (D3) smaller than said second diameter (D2) in such a way as to be able to pass through the aperture ( 7 ) of the first securing foot ( 6 ).

The invention relates to the turbine engines sector, and more particularly that of inter-vane platforms for support disks for vanes of turbine engine fans.

The fans of a turbine engine, of which the vanes present a curvilinear foot, generally comprise support disks for vanes which are equipped with detachable inter-vane platforms intended to optimize the flow of air between the vanes, and, more precisely, to reconstitute the dynamic profile of the internal jet at the level of the vanes, in particular if they are of large chord.

A detachable platform usually comprises a deflecting part, of which the lower face comprises at least one securing foot (and more generally two or three), intended to allow for its connection to another securing foot of a support disk by means of a securing pin.

The securing pins conventionally have the shape of a rod provided with a first threaded part, having a first diameter, and extended by a second part that constitutes a head, having a second diameter greater than the first. In order to connect the securing feet to one another, the securing pin is first secured on the securing foot of the support disk, immobilizing it by means of a nut. The platform is then slid in the direction of the securing pin until the head of said pin penetrates into the aperture in the securing foot of the platform. The head of the pin is then lodged in the aperture of the securing foot of the platform, while projecting out from it. Due to this method of assembly, the nut is hard to access.

Because the detachable platform is subjected to a centrifugal force, each securing pin undergoes flexure and shear stress. Due to the method of connection and function of the securing pin, only the threaded section of the rod operates simultaneously in flexure and shear. In consequence, it is the part of the securing pin that has the smallest diameter, and therefore the lowest strength, which is subjected to the highest stress.

In order to improve the strength of the pins, it might be possible to envisage increasing the diameters of their various parts, but this is not possible for reasons of space.

The object of the invention is therefore to overcome all or part of the above disadvantages.

To achieve this, the invention proposes an inter-vane platform for a vane support disk of a fan of a turbine engine, comprising a deflecting part, in turn comprising a lower face provided with at least one first securing foot (or flange), comprising at least one aperture for the passage of a securing pin intended to connect it between two adjacent vanes to a second securing foot (or flange) of the support disk.

This platform, made preferably of a metal or composite material, is characterized by the fact that each securing pin comprises a rod, provided with a threaded first part, which has a first selected diameter intended to receive a bolt intended for the connection, and a second part comprising a first sub-part serving to extend the first part and having a second diameter, greater than the first diameter, and a second sub-part extending the first sub-part and having a third diameter smaller than the second diameter, in such a way as to be able to pass through the aperture of the first securing foot.

The first sub-part of the rod is therefore interleaved between the first and second securing feet, including when it is subjected to stress in flexure. This arrangement is therefore optimum, since it allows for the flexural stresses to be supported by the portion of the rod that has the greatest diameter and shear stresses in comparison with the two other portions.

In addition to this, the diameters of each of the portions of the rod can also be selected as a function of the stresses specific to the environment of the platform.

Accordingly, a rod can be envisaged which comprises first and third diameters that are substantially identical or different.

In addition to this, the aperture in the first securing foot preferably has an internal diameter that is substantially equal, by higher value, to the third diameter, so that the second sub-section of the rod is in close contact with said first securing foot. In order to improve this contact still further, the aperture of the first securing foot may accommodate a disconnected element (or sleeve or another insert), defining the internal diameter.

The invention likewise relates to a vane support disk comprising a plurality of inter-vane platforms of the type presented above and interlaced respectively between the pairs of adjacent vanes.

Other features and advantages of the invention will become apparent on examination of the detailed description below and of the appended drawings, in which:

FIG. 1 shows in diagrammatic form a part of a vane support disk in a face view,

FIG. 2 shows in diagrammatic form, in a medial sectional view, an embodiment of an inter-vane platform according to the invention,

FIG. 3 shows in detail, in diagrammatic form, in a medial sectional view, a part of the platform of FIG. 2, and

FIG. 4 is a variant of the part of the platform shown in FIG. 3.

The appended drawings can serve not only to supplement the invention, but also contribute to its definition, as applicable.

The invention relates to an inter-vane platform intended to equip a vane support disk for a fan of a turbine engine equipped with vanes with curvilinear feet (also referred to as “wide chord” vanes).

As is partially illustrated in FIG. 1, a vane support disk 1 is an element of a fan (not shown), mounted on a rotor shaft, and on which are fixed a plurality of vanes 2, with curvilinear feet, and a plurality of detachable inter-vane platforms 3, preferably metallic (for example made of aluminum), or of a composite material.

Each detachable platform 3 is, more precisely, installed on the support disk 1, between two adjacent vanes 2, in such a way as to restore the aerodynamic profile of the internal jet at the level of the vanes.

A platform 3 according to the invention, as illustrated in diagrammatic form in FIG. 2, comprises a deflecting part 4, comprising a lower face 5 provided with at least one securing foot. In the example illustrated, the platform 3 comprises a first securing foot (or flange) 6, provided with a first aperture 7 for the passage of a first securing pin 8, and a second securing foot (or flange) 9 provided with a second aperture 10 for the passage of a second securing pin 11.

The first securing pin 8 is intended to connect the first securing foot 6 to a third securing foot (or flange) 12 of an element 13 of the support disk 1, which for this purpose is provided with a third aperture 14. Likewise, the second securing pin 11 is intended to connect the second securing foot 9 to a fourth securing foot (or flange) 15 of the element 13, which is provided for this purpose with a fourth aperture 16.

As is better illustrated in FIG. 3, each securing pin 8 or 11 comprises a rod 17 provided with a first threaded part 18, having a first selected diameter D1, and a second part 19 (or head with a shoulder) comprising a first sub-part 20 (or collar) extending the first threaded part 18, having a second diameter D2, greater than the first diameter D1, and extended by a second sub-part 21 (or head), having a third diameter D3, smaller than the second diameter D2.

Each securing pin 8 and 11 additionally comprises a nut 22, intended to be screwed onto the first threaded part 20 of the rod 17 in such a way as to render it as one piece with one of the securing feet 12 or 15 of the element 13.

The first diameter D1 of the first threaded part 18 of the rod 17 (for example, of the first securing pin 8) is substantially equal, by lower value, to the diameter of the third aperture 14 of the third securing foot 12 of the element 13. In addition to this, the third diameter D3 of the second sub-section 21 of the rod 17 (for example, of the first securing pin 8) is substantially equal, by lower value, to the inner diameter of the first aperture 7 of the first securing foot 6 of the platform 13.

In the example shown, the first aperture 7 accommodates a sleeve (or insert) 23, preferably metallic, intended to avoid the second sub-part 21 (or head) from being damaged due to the stresses imposed on it.

Thanks to this arrangement, once the rod 17 is installed its first sub-part 20 is located interlaced between a “front” face (or in this case the left-hand side) of a securing foot (for example, the third 12) of the element 13, and a “rear” face (in this case the right-hand side) of a securing foot (for example, the first 6) of the platform 3. More precisely, the first sub-part 20 (or collar) defines the first and second support surfaces, substantially flat, intended to support one another respectively against the front face of the (third) securing foot (12) and the rear face of the (first) securing foot (6), which are substantially flat, at least locally.

At the same time, the first threaded part 18 of the rod 17 passes through the (third) aperture (14) of the (third) securing foot (12) and opens to the outside of the side of its rear face, and the second sub-part 21 passes through the (first) aperture of the (first) securing foot (6) and opens to the outside of the side of its front face. The front face (substantially flat) of the nut 22, screwed onto the first threaded part 18 of the rod 17, is therefore supported on the rear face of the (third) securing foot (12) of the element 13, which is substantially flat, at least locally.

Because the platform 3 is principally subject to a centrifugal force, represented by the arrow F, it is therefore, thanks to the invention, the first sub-part 20 (or collar) of its securing pins 8 and 11 which is subjected to the flexure stresses, while the first threaded part 18 and the second sub-part 21 of said securing pins undergo shearing stresses.

This is particularly advantageous since it is the first sub-part 20 (or collar) which has the largest diameter (D2) within the rod 17 that supports the greatest stresses. In consequence, the diameter of the collar 20 is preferably chosen to be as large as possible. The same applies to its thickness (according to the axis of the pin).

In addition to this, thanks to the invention, it is possible to choose diameters (D1 to D3) of the rods 17 of the securing pins 8 and 11 as a function of the stresses specific to the environment of the platform 3. Accordingly, as illustrated in FIG. 2, the first diameter D1 and the third diameter D3 can be chosen to be substantially identical, or, as a variant, as illustrated in FIG. 4, the first diameter D1 and the third diameter D3 may be chosen to be different, in order to accommodate the shear stresses satisfactorily.

The invention is not limited to the embodiments of the inter-vane platform and vane support disk described above, only by way of example, but encompasses all the variants which the person skilled in the art could envisage within the framework of the claims hereafter. 

1. Inter-vane platform (3) for a support disk (1) of vanes (2) of a fan of a turbine engine, said platform (3) comprising a deflecting part (4) comprising a lower face (5) provided with at least one securing foot (6,9) provided with at least one aperture (7,10) for the passage of a securing pin (8,11) intended to link it to a second securing foot (12,15) of said support disk (1) between two adjacent vanes (2), characterized in that said securing pin (8,11) comprises a rod (17) provided with a first threaded part (18), having a first diameter (D1) chosen and suitable for accommodating a nut (22) for the purpose of this connection, and a second part (19) comprising a first sub-part (20) extending said first part (18), having a second diameter (D2) greater than said first diameter (), and intended to be interlaced between said first (6,9) and second (12,15) securing feet, and a second sub-part (21) extending said first sub-part (20) and having a third diameter (D3) smaller than said second diameter (D2) in such a way as to be able to pass through said aperture (7,10) of the first securing foot (6,9).
 2. Platform according to claim 1, characterized in that said second diameter (D2) is chosen as a function of the flexural strength that said securing pin (8,11) must support.
 3. Platform according to one of claims 1 and 2, characterized in that said first (D1) and third (D3) diameters are chosen as a function of the shear stresses that said securing pin (8,11) must resist.
 4. Platform according to one of claims 1 to 3, characterized in that said aperture (7,10) of the first securing foot (6,9) has an internal diameter substantially equal, by higher value, to said third diameter (D3).
 5. Platform according to claim 4, characterized in that said aperture (7,10) of the first securing foot (6,9) accommodates a detached element (23) defining said internal diameter.
 6. Platform according to one of claims 1 to 5, characterized in that said first (D1) and third (D3) diameters are identical.
 7. Platform according to one of claims 1 to 5, characterized in that said first (D1) and third (D3) diameters are different.
 8. Platform according to one of claims 1 to 7, characterized in that said nut (22) comprises a support face that is substantially flat, intended to be supported on a first face of said second securing foot (12,15), substantially flat, at least locally, and in that said first sub-part (20) defines the first and second substantially flat support surfaces intended to be supported respectively against a second face of said second securing foot (12,15) and a first face of said first securing foot (6,9), substantially flat, at least locally.
 9. Platform according to one of claims 1 to 8, characterized in that it is made of a metallic material.
 10. Platform according to one of claims 1 to 8, characterized in that it is made of a composite material.
 11. Vane support disk (1), characterized in that it comprises a plurality of inter-vane platforms (3) according to one of the foregoing claims, interlaced respectively between pairs of adjacent vanes (2). 